Valve needle assembly and electronic expansion valve including the same

Abstract

The present disclosure provides a valve needle assembly and an electronic expansion valve including the valve needle assembly. The valve needle assembly includes: a guide sleeve; a valve needle disposed in the guide sleeve and capable of moving axially relative to the guide sleeve; an elastic element disposed in the guide sleeve and adapted to apply a force to the valve needle; and a pressing block disposed in the guide sleeve and located between the elastic element and the valve needle to transmit the force of the elastic element to the valve needle. Wherein, the pressing block is sealingly connected to the guide sleeve, and the valve needle is sealingly connected to the guide sleeve. With the valve needle assembly and the electronic expansion valve according to the present invention, it is possible to prevent the electronic expansion valve from opening prematurely under the action of fluid and causing internal leakage, and ensure that the fluid flow rate through the electronic expansion valve can be accurately controlled even in the reverse flow state of the fluid.

Description

Technical Field

[0001] The present invention relates to a valve needle assembly and an electronic expansion valve including the valve needle assembly. Background Art

[0002] The content of this part only provides background information related to the present invention, which may not constitute prior art.

[0003] The electronic expansion valve is an important component in the refrigeration system, which adjusts the flow rate of the working fluid by regulating the opening degree of the valve needle. Generally, the electronic expansion valve mainly includes a driving component and an executing component. The driving component includes a stepping motor and a corresponding threaded screw mechanism, and the executing component includes a valve needle assembly and a valve seat that cooperates with it. In a traditional electronic expansion valve, the stepping motor and the threaded screw mechanism directly drive the valve needle assembly to open or close the electronic expansion valve, thereby regulating the flow rate of the refrigerant fluid. To ensure the reliable and efficient operation of the refrigeration system, the electronic expansion valve needs to effectively ensure its basic performance and reliability.

[0004] Currently, the valve needle assembly mainly adopts two design schemes: rigid connection and flexible connection.

[0005] The valve needle assembly with rigid connection mainly uses rigid connection methods such as interference fit to connect and assemble the relevant parts in the valve needle assembly. In actual work, there are usually position deviations caused by part processing or assembly. The valve needle assembly with rigid connection cannot be adjusted according to the actual working conditions. Therefore, the valve needle assembly is prone to hard contact with other components, resulting in jamming, which causes the electronic expansion valve to not function properly. To avoid the occurrence of the above phenomena as much as possible, higher requirements are put forward for the manufacturing precision of each part of the electronic expansion valve, the performance of the motor, etc., which increases the manufacturing cost of the electronic expansion valve.

[0006] The valve needle assembly with flexible connection provides a solution to the above problems. The valve needle assembly with flexible connection mainly uses elastic parts such as springs to enable the valve needle to adjust its position axially and radially, thus effectively reducing the adverse effects of position deviations caused by part processing or assembly. Due to its flexibility, the valve needle forms a soft contact with other components, and the resistance exerted on the movement of the valve needle is small, so the requirements for the motor performance are low, and the jamming phenomenon can be effectively reduced.

[0007] On the other hand, with the gradual development and application of electric buses, heat pumps, etc., the actual system has an increasingly strong demand for the bidirectional function of the electronic expansion valve. However, the existing flexible valve needle assembly cannot meet the basic performance requirements in the reverse state of the bidirectional electronic expansion valve due to its own structural limitations, which will have an adverse impact on the actual application of the bidirectional refrigeration system.

[0008] Therefore, there is a need to solve the above deficiencies of the electronic expansion valve in the prior art. Summary of the Invention

[0009] An object of the present invention is to provide a valve needle assembly and an electronic expansion valve, which can prevent the electronic expansion valve from opening prematurely under the action of fluid and causing internal leakage, and ensure that the fluid flow rate through the electronic expansion valve can be accurately controlled even in the reverse flow state of the fluid.

[0010] Another object of the present invention is to provide a valve needle assembly and an electronic expansion valve, which can enhance the sealing force between the valve needle and the valve seat in the forward flow state of the fluid and prevent fluid leakage.

[0011] According to one aspect of the present disclosure, there is provided a valve needle assembly, the valve needle assembly comprising: a guide sleeve; a valve needle disposed in the guide sleeve and capable of moving axially relative to the guide sleeve; an elastic element disposed in the guide sleeve and adapted to apply a force to the valve needle; and a pressure block disposed in the guide sleeve and located between the elastic element and the valve needle to transmit the force of the elastic element to the valve needle; characterized in that the pressure block is sealingly connected to the guide sleeve, and the valve needle is sealingly connected to the guide sleeve.

[0012] According to one aspect of the present disclosure, the valve needle is formed with a fluid passage, and when fluid flows through the fluid passage and acts on the pressure block, the pressure block moves away from the valve needle, thereby forming a fluid chamber between the pressure block and the valve needle.

[0013] According to one aspect of the present disclosure, a first seal for providing radial sealing is provided between the pressure block and the guide sleeve, and a second seal for providing radial sealing is provided between the valve needle and the guide sleeve.

[0014] According to one aspect of the present disclosure, the first seal is partially disposed in the pressure block and thus moves axially as the pressure block moves axially, and / or the second seal is partially disposed in the valve needle and thus moves axially as the valve needle moves axially.

[0015] According to one aspect of the present disclosure, the pressing block is formed with an arc-shaped surface at the first end facing the valve needle. In a state where the pressing block moves away from the valve needle, the fluid chamber is formed between the arc-shaped surface and the surface of the valve needle opposite to the arc-shaped surface; or the pressing block is formed with a flat surface at the first end facing the valve needle, and the pressing block has a recess opening towards the valve needle, and the flat surface is located radially outside the recess. In a state where the pressing block moves away from the valve needle, the fluid chamber is formed between the flat surface and the recess and the surface of the valve needle opposite to the first end.

[0016] According to one aspect of the present disclosure, the guide sleeve includes a first section and a second section. The inner diameter of the second section is larger than that of the first section, so as to form a step portion between the first section and the second section. The step portion is configured to limit the maximum distance that the pressing block can move towards the first section.

[0017] According to one aspect of the present disclosure, the fluid passage axially penetrates through the valve needle and is formed in the center of the valve needle.

[0018] According to another aspect of the present disclosure, there is provided an electronic expansion valve including the above-mentioned valve needle assembly.

[0019] According to another aspect of the present disclosure, the electronic expansion valve includes a valve seat. The valve seat is provided with a valve hole. The valve needle cooperates with the valve hole to adjust the flow rate of the fluid flowing through the electronic expansion valve. And, the cross-sectional area of the first end portion of the valve needle facing the pressing block is larger than the cross-sectional area of the valve hole.

[0020] According to another aspect of the present disclosure, the electronic expansion valve includes a first pipeline and a second pipeline. Any one of the first pipeline and the second pipeline serves as an inlet pipeline and the other of the first pipeline and the second pipeline serves as an outlet pipeline.

[0021] According to another aspect of the present disclosure, the guide sleeve is provided with a passage that can fluidly connect the elastic element chamber provided with the elastic element in the guide sleeve to the first pipeline and the second pipeline. The first pipeline and the valve needle assembly are arranged on opposite sides of the valve seat.

[0022] The valve needle assembly of the present invention can effectively limit the relative movement of the valve needle relative to the valve hole, thereby preventing the valve needle of the electronic expansion valve from prematurely opening the valve hole under the action of fluid force and causing internal leakage, ensuring that the electronic expansion valve can accurately control the opening of the valve hole in the state of reverse fluid flow, so that the electronic expansion valve can work normally in both bidirectional flow states. Description of the Drawings

[0023] Embodiments of the present invention will be described below by way of example only with reference to the accompanying drawings, in which like features or components are denoted by like reference numerals and the drawings are not necessarily drawn to scale, and in the drawings:

[0024] Figure 1 is a sectional view showing an electronic expansion valve according to the prior art;

[0025] Figure 2 and Figure 3 is a schematic view showing an electronic expansion valve according to a first embodiment of the present application;

[0026] Figure 4 is a schematic view showing a valve needle assembly and a valve seat of an electronic expansion valve according to a first embodiment of the present application;

[0027] Figure 5 is another schematic view showing a valve needle assembly and a valve seat of an electronic expansion valve according to a first embodiment of the present application;

[0028] Figure 6 is a schematic view showing a valve needle assembly and a valve seat of an electronic expansion valve according to a second embodiment of the present application; and

[0029] Figure 7 is another schematic view showing a valve needle assembly and a valve seat of an electronic expansion valve according to a second embodiment of the present application. Detailed Embodiments

[0030] The following descriptions of the embodiments of the present disclosure are merely exemplary and in no way limit the present disclosure and its application or use. The same reference numerals are used to denote the same components in the respective drawings, and thus the construction of the same components will not be described repeatedly.

[0031] In the description of the embodiments of the present invention, the orientation terms related to "upper" and "lower" are described based on the upper and lower positions of the views shown in the drawings, and the "forward" and "reverse" are defined according to the flow direction of the fluid. In the actual application of the electronic expansion valve or the valve needle assembly, the positional relationship of "upper" and "lower" and the flow direction of "forward" and "reverse" used herein can be defined according to the actual situation, and these relationships and directions can be reversed with each other.

[0032] Figure 1FIG. 0 is a sectional view showing an electronic expansion valve 100 according to the prior art. The electronic expansion valve 100 mainly includes a stepping motor 110, a valve needle assembly 120, and a valve seat 130 that cooperates with the valve needle assembly 120. The stepping motor 110 cooperates with a coil 111, and an armature 112 may be disposed inside the coil 111. Inside the electronic expansion valve 100, a mandrel 113 is provided that is relatively fixed in the circumferential rotation direction of the stepping motor 110. The valve needle assembly 120 includes a guide sleeve 121, a valve needle 122, a pressing block assembly 123, and a spring 124. Among them, the valve needle 122, the pressing block assembly 123, and the spring 124 are disposed inside the guide sleeve 121. The upper end of the guide sleeve 121 is connected to the mandrel 113. The mandrel 113 can convert the rotational movement of the stepping motor 110 into the movement of the valve needle assembly 120 in the up and down direction (axial direction), so that the lower end of the valve needle 122 cooperates with the valve hole 132 on the valve seat 130 to adjust the flow rate of the fluid passing through the electronic expansion valve.

[0033] In the valve needle assembly 120, the spring 124 applies a force to the valve needle 122 and acts on the valve needle 122 via the pressing block assembly 123. The valve needle 122 can axially move inside the guide sleeve 121 under the action of the spring 124. When there is a positional deviation caused by manufacturing or assembly tolerances in the electronic expansion valve 100, the valve needle 122 can move upward inside the guide sleeve 121 against the elastic force of the spring 123, thereby providing axial flexibility and radial flexibility and avoiding jamming. Therefore, the requirements for the manufacturing precision and assembly precision of each component of the electronic expansion valve can be reduced.

[0034] When the electronic expansion valve 100 is used as a two-way electronic expansion valve, in the state of forward fluid flow, when the valve needle assembly 120 opens the valve hole 132 on the valve seat 130, the fluid flows into the electronic expansion valve 100 from the second pipeline 154 and flows through the valve hole 132, and then is discharged from the electronic expansion valve 100 via the first pipeline 152. In the state of reverse fluid flow, when the valve needle assembly 120 opens the valve hole 132 on the valve seat 130, the fluid flows into the electronic expansion valve 100 from the first pipeline 152 and flows through the valve hole 132, and then is discharged from the electronic expansion valve 100 via the second pipeline 154.

[0035] In the state of reverse fluid flow, especially in the case of a large-diameter valve, the fluid exerts an upward force on the lower end of the valve needle 122, and this force may overcome the force of the spring 124 and cause the valve needle 122 to move upward. Specifically, in the valve needle assembly 120, the upward movement of the valve needle 122 against the force of the spring 124 is restricted by the stiffness of the spring 124. However, the stiffness of the spring 124 cannot be set too large, otherwise the meaning of providing axial flexibility and radial flexibility through the flexible connection will be lost. Therefore, when it is not yet required to open the valve hole 132 on the valve seat 130, the valve needle 122 may move upward by too large a distance against the force of the spring 124 under the action of the fluid, causing the valve hole 132 to open in advance, resulting in internal leakage, and thus the flow rate of the fluid flowing through the electronic expansion valve cannot be accurately controlled in the state of reverse fluid flow.

[0036] In view of the above problems, the inventor of the present invention proposed the inventive concept. The present invention ensures that the valve needle stably closes the valve hole by setting a fluid chamber in the valve needle assembly and utilizing the fluid force in the fluid chamber, avoiding the occurrence of internal leakage due to the premature opening of the valve hole on the valve seat in the state of reverse fluid flow of the electronic expansion valve, so that the electronic expansion valve can accurately control the flow rate of the fluid flowing through the electronic expansion valve in both the forward state and the reverse state.

[0037] The following will Figures 2 to 5 describe the electronic expansion valve 200 according to the first embodiment of the present invention. The electronic expansion valve 200 mainly includes a drive assembly, a valve needle assembly 220, and a valve seat 230. The drive assembly may include a stepper motor having a rotor, and a mandrel 213 is fixedly connected to the rotor such that the mandrel 213 rotates integrally with the rotor. The electronic expansion valve 200 may further include a first pipeline 252 and a second pipeline 254. Either one of the first pipeline 252 and the second pipeline 254 may be used as an inlet pipeline, and the other may be used as an outlet pipeline. That is to say, the electronic expansion valve 200 may be used as a two-way electronic expansion valve. As Figure 2 shown, the first pipeline 252 and the valve needle assembly 220 may be respectively disposed on the upper and lower sides of the valve seat 230.

[0038] Next, the structure and working principle of the valve needle assembly 220 will be described in detail. As Figure 3As shown, the valve needle assembly 220 may include a guide sleeve 221, a valve needle 222, a pressure block 223, and an elastic element such as a spring 224. The upper end of the guide sleeve 221 is connected to the mandrel 213. The rotational movement of the mandrel 213 is converted into the up-and-down movement (axial direction) of the guide sleeve 221. Since the valve needle 222, the pressure block 223, and the spring 224 are all accommodated in the guide sleeve 221, the entire valve needle assembly 220 also moves axially accordingly. The spring 224 is configured to apply a force to the valve needle 222. The pressure block 223 is disposed between the spring 224 and the valve needle 222 and is adapted to transmit the force of the spring 224 to the valve needle 222. On the one hand, the valve needle 222 can move downward relative to the guide sleeve 221 under the action of the spring 224, and in the case of being affected by, for example, the reverse-flowing fluid, the valve needle 222 can also move upward relative to the guide sleeve 221 against the force of the spring 224. The pressure block 223 and the valve needle 222 move independently of each other, and a fluid chamber P can be formed therebetween. Specifically, the valve needle 222 may be formed with a fluid passage 226. When the fluid flows upward through the fluid passage 226 and acts on the pressure block 223, the pressure block 223 moves upward away from the valve needle 222, thereby forming a fluid chamber between the pressure block 223 and the valve needle 222. When there is a positional deviation caused by manufacturing or assembly tolerances in the electronic expansion valve 200, the valve needle 222 can move upward within the guide sleeve 221 against the biasing force of the spring 224, thereby providing axial flexibility and radial flexibility to avoid jamming. The pressure block 223 is sealingly connected to the guide sleeve 221, and the valve needle 222 is also sealingly connected to the guide sleeve 221. In this application, the sealing connection means that the two components are in sealing contact and allow the components to move axially relative to each other. Thus, on the one hand, when the fluid flows in the forward direction, the sealing connection between the pressure block 223, the valve needle 222, and the guide sleeve therebetween can prevent the fluid from leaking through the passage 225 and the fluid passage 226 when the valve needle 222 is not opened; on the other hand, when the fluid flows in the reverse direction, through this sealing connection, the fluid can be sealed in the fluid chamber P between the pressure block 223 and the valve needle 222 to prevent the fluid from flowing upward through the passage 225 and leaking.

[0039] As Figure 4As shown, a first seal S1 providing radial sealing may be provided between the briquette 223 and the guide sleeve 221, and a second seal S2 providing radial sealing may be provided between the valve needle 222 and the guide sleeve 221. For example, a first groove may be formed in the briquette 223, and the first seal S1 is at least partially received in the first groove, whereby the first seal S1 can move axially relative to the guide sleeve 221 together with the briquette 223. For example, a second groove may be formed in the valve needle 222, and the second seal S2 is at least partially received in the second groove, whereby the second seal S2 can move axially relative to the guide sleeve 221 together with the valve needle 222. The first seal S1 and the second seal S2 may be annular seals to provide sealing around the entire outer periphery of the valve needle and the briquette.

[0040] The briquette 223 may have an arc-shaped surface formed at a first end facing the valve needle 222 (i.e., Figure 4 and Figure 5 the lower end in ). At this time, a point contact may be formed between the briquette 223 and the valve needle 222, so as to increase the rotational freedom of the valve needle 222, thereby facilitating the centering of the valve needle 222 with the valve hole in the valve seat 230 and facilitating the achievement of good sealing between the valve needle 222 and the valve seat 230. In addition, the briquette 223 may have a flat surface formed at a second end opposite to the first end (i.e., Figure 4 and Figure 5 the upper end in ), which is convenient for the spring 224 to stably abut against the briquette and uniformly apply an elastic biasing force to the briquette and the valve needle.

[0041] The fluid passage 226 of the valve needle 222 may axially pass through the valve needle 222 at the center of the valve needle, whereby the portions of the valve needle 222 on both sides of the fluid passage are symmetric, so that the valve needle 222 can move axially more stably without tilting. The valve needle 222 may have a first end portion 222a facing the briquette 223 (i.e., Figure 4 and Figure 5 the upper end portion in ) and a second end portion 222b opposite to the first end portion 222a (i.e., Figure 4 and Figure 5 the lower end portion in ). The cross-sectional area of the first end portion 222a of the valve needle 222 may be larger than the cross-sectional area of the valve hole 232 of the valve seat 230. Generally, both the valve hole and the valve needle have a circular cross-section. In this case, the diameter of the first end portion of the valve needle is larger than the diameter of the valve hole. Here, it should be noted that the cross-section in this application refers to the cross-section perpendicular to the axial direction. The second end portion 222b of the valve needle 222 is in a truncated cone shape that fits with the valve hole 232 on the valve seat 230, and its taper can be set according to the flow characteristics of the electronic expansion valve.

[0042] An inwardly protruding flange is formed at the upper end of the guide sleeve 221. One end of the spring 224 abuts against the flange of the guide sleeve 221, and the other end of the spring 224 presses against the pressure block 223. A retaining ring 227 is provided at the lower end of the guide sleeve 221. The retaining ring 227 and the guide sleeve 221 are fixedly connected together, for example, by an interference fit. The valve needle 222 is held in the lower end of the guide sleeve 221 by the retaining ring 227. Further, the guide sleeve 221 may be provided with a passage 225 that communicates the spring chamber in the guide sleeve 221 where the spring 224 is disposed with the first pipeline 252 and the second pipeline 254.

[0043] When the electronic expansion valve 200 is in the open state, as Figure 2 shown, the valve needle 222 moves upward away from the valve hole 232, whereby fluid can flow through the valve hole 232. When the fluid moves forward, as Figure 2 indicated by the solid arrow, the fluid flows into the electronic expansion valve 200 from the second pipeline 254, then flows into the first pipeline 252 via the valve hole 232, and leaves the electronic expansion valve from the first pipeline 252. And at this time, a part of the fluid flowing into the spring chamber can be discharged from the first pipeline 252 through the passage 225, so as to reduce the downward acting force of the fluid and facilitate the opening of the valve needle. When the fluid moves in the reverse direction, as Figure 2 indicated by the dashed arrow, the fluid flows into the electronic expansion valve 200 from the first pipeline 252, and then flows into the second pipeline 254 via the valve hole 232 and leaves the electronic expansion valve from the second pipeline 254.

[0044] When the electronic expansion valve 200 is in the closed state, as Figures 3 - 5 shown, the valve needle 222 closes the valve hole 232 to prevent fluid from flowing through the valve hole 232. When the fluid moves forward, as Figure 3 and Figure 4As shown, fluid flows from the second pipeline 254 into the electronic expansion valve 200, and flows into the spring chamber provided with the spring 224 of the guide sleeve 221 through the channel 225 of the guide sleeve 221. The fluid flowing into the spring chamber of the guide sleeve 221 exerts a downward pressure on the pressure block 223. The pressure block 223 abuts against the valve needle 222 downward under the action of the spring and the fluid. Thus, the downward pressure exerted by the fluid and the downward biasing force exerted by the spring act on the valve needle 222 together via the pressure block 223, so that the valve needle 222 firmly abuts against the valve seat 230 and seals the valve hole 232. By means of the channel 225, the sealing force of the valve needle towards the valve hole can be increased, preventing fluid leakage and ensuring that the fluid flow rate through the electronic expansion valve can be accurately controlled. And as described above, in the state of forward fluid flow, when the valve needle assembly 220 is lifted upward to open the valve hole 232, the fluid flowing into the spring chamber can be discharged from the first pipeline 252 through the channel 225, facilitating the upward movement of the valve needle and the pressure block. In the valve needle assembly 220, since the first seal S1 and the second seal S2 provide double seals between the pressure block, the valve needle and the guide sleeve, the fluid flowing into the spring chamber of the guide sleeve will not flow downward between the pressure block and the valve needle and then flow out through the fluid channel 226 of the valve needle. Thus, the first seal S1 and the second seal S2 can prevent fluid leakage.

[0045] When the fluid flows in the reverse direction, referring to Figure 3 and Figure 5 , the fluid flows from the first pipeline 252 (shown in Figure 3 ) into the upper part of the valve needle 222 through the channel 226 of the valve needle 222 and impacts the pressure block 223. The pressure block 223 moves upward under the impact force of the upward flowing fluid, overcoming the biasing force of the spring 224, so that a fluid chamber P containing fluid is formed between the pressure block 223 and the valve needle 222 (shown in Figure 5 ). At this time, the valve needle 222 receives a downward acting force exerted by the fluid contained in the fluid chamber P at the upper end 222a, and the valve needle 222 receives an upward impact force exerted by the fluid contained in the valve hole 232 at the lower end 222b. Since the cross-sectional area of the upper end 222a is larger than the cross-sectional area of the valve hole 232, the valve needle 222 is generally subjected to a downward acting force and is firmly held against the valve seat 230 and seals the valve hole 232. Thus, the above-mentioned internal leakage phenomenon can be avoided, enabling the electronic expansion valve 200 to work normally in the state of reverse fluid flow.

[0046] The following will be combined with Figure 6 and Figure 7Describe the valve needle assembly 320 according to the second embodiment of the present invention and the electronic expansion valve including the same. Except for the valve needle assembly 320, the other structures of the electronic expansion valve including the valve needle assembly 320 are substantially the same as or similar to the structure of the electronic expansion valve 200, and will not be described repeatedly herein. Similar to the valve needle assembly 220, the valve needle assembly 320 may also include a guide sleeve 321, a valve needle 322, a pressing block 323, and an elastic element (for example, a spring 324). Since the valve needle 322 and the spring 324 of the valve needle assembly 320 according to the second embodiment of the present invention are exactly the same in structure and function as the valve needle 222 and the spring 224 of the valve needle assembly 220 according to the first embodiment of the present invention, they will not be elaborated herein. The guide sleeve 321 and the pressing block 323 of the valve needle assembly 320 will be specifically described below.

[0047] The guide sleeve 321 may include a first section 321a and a second section 321b, and the inner diameter of the second section 321b is larger than the inner diameter of the first section 321a, so as to form a step portion 328 between the first section 321a and the second section 321b. The step portion 328 may constitute a stop portion to limit the maximum distance that the pressing block 323 can move toward the first section 321a, thereby preventing the spring 324 from being over-compressed. As Figure 7 shown, the step portion 328 may be provided below the channel 325 of the guide sleeve 321, so as to prevent the fluid chamber P from being in fluid communication with the channel 325.

[0048] The pressing block 323 may be formed with a recess opening toward the valve needle 322, and a flat surface may be formed on the radially outer side of the recess of the pressing block 323. The recess of the pressing block 323 may facilitate the movement of the pressing block 323 away from the valve needle 322, preventing the pressing block 323 from being completely attached to the valve needle 322 and preventing the formation of the fluid chamber P between the pressing block 323 and the valve needle 322.

[0049] When the fluid moves forward, as Figure 6As shown, the fluid flows into the spring chamber accommodating the spring 324 of the guide sleeve 321 through the channel 325 of the guide sleeve 321. The fluid flowing into the spring chamber of the guide sleeve 321 exerts a downward pressure on the pressure block 323. The pressure block 323 abuts against the valve needle 322 downward under the action of the spring and the fluid. Thus, the downward pressure exerted by the fluid and the downward biasing force exerted by the spring act on the valve needle 322 jointly via the pressure block 323, so that the valve needle 322 firmly abuts against the valve seat 230 and seals the valve hole 232. By means of the channel 325, the sealing force of the valve needle towards the valve hole can be increased, preventing fluid leakage and ensuring that the fluid flow rate through the electronic expansion valve can be accurately controlled. Moreover, when the valve needle assembly 320 is lifted upward to open the valve hole 232, the fluid flowing into the spring chamber can be discharged through the channel 325, facilitating the upward movement of the valve needle and the pressure block. In the valve needle assembly 320, double seals can also be provided by using the first seal S1 and the second seal S2. Therefore, the fluid flowing into the guide sleeve will not flow downward between the pressure block and the valve needle and then flow out through the fluid channel 326 of the valve needle. Thus, the first seal S1 and the second seal S2 can prevent fluid leakage.

[0050] When the fluid flows in the reverse direction, referring to Figure 7 , the fluid flows into the upper part of the valve needle 322 through the channel 326 of the valve needle 322 and impacts the pressure block 323. The pressure block 323 moves upward under the impact force of the fluid flowing upward, overcoming the biasing force of the spring 324, so that a fluid chamber P accommodating the inflowing fluid is formed between the pressure block 323 and the valve needle 322. At this time, the valve needle 322 receives a downward acting force exerted by the fluid accommodated in the fluid chamber P at the upper end portion 322a, and the valve needle 322 receives an upward impact force exerted by the fluid accommodated in the valve hole 232 at the lower end portion 322b. Since the cross-sectional area of the upper end portion 322a of the valve needle 322 is larger than the cross-sectional area of the valve hole 232, the valve needle 322 is generally subjected to a downward acting force and is firmly held against the valve seat 330 and seals the valve hole 332. Thus, the above-mentioned internal leakage phenomenon can be avoided, enabling the electronic expansion valve to work properly even in the state of reverse fluid flow.

[0051] Although it is exemplarily shown in the embodiments of the present application that the guide sleeve is formed with a channel fluidly communicating with the second pipeline, those skilled in the art should understand that the channel can also be omitted and the guide sleeve can be made not fluidly communicating with the second pipeline. In addition, although only the guide sleeve formed with a stepped portion is shown in the valve needle assembly 320, it should be understood that the guide sleeve 221 of the valve needle assembly 220 can also be formed with a stepped portion.

[0052] In the foregoing, exemplary embodiments of the present invention have been described in detail, but it should be understood that the present invention is not limited to the specific embodiments described and illustrated above. Without departing from the gist and scope of the present invention, those skilled in the art can make various modifications and variations to the present invention. All such modifications and variations fall within the scope of the present invention. Moreover, all components described herein can be replaced by other technically equivalent components.

Claims

1. An electronic expansion valve, comprising: A valve needle assembly (220, 320), the valve needle assembly comprising: a guide sleeve (221, 321); a valve needle (222, 322), the valve needle being disposed in the guide sleeve and capable of moving axially relative to the guide sleeve; an elastic element (224, 324), the elastic element being disposed in the guide sleeve and adapted to apply a force to the valve needle; and a pressing block (223, 323), the pressing block being disposed in the guide sleeve and located between the elastic element and the valve needle to transmit the force of the elastic element to the valve needle; and A valve seat (230), the valve seat being provided with a valve hole (232), the valve needle (222, 322) cooperating with the valve hole to regulate the flow rate of the fluid flowing through the electronic expansion valve, Characterized in that, the pressing block is sealingly connected to the guide sleeve, and the valve needle is sealingly connected to the guide sleeve, The valve needle (222, 322) is formed with a fluid passage (226, 326), in the case where the fluid flows through the fluid passage and acts on the pressing block, the pressing block moves away from the valve needle, so as to form a fluid chamber (P) between the pressing block and the valve needle, The cross-sectional area of the first end (222a, 322a) of the valve needle (222, 322) facing the pressing block (223, 323) is larger than the cross-sectional area of the valve hole (232).

2. The electronic expansion valve according to claim 1, characterized in that, A first seal (S1) providing radial seal is provided between the pressing block (223, 323) and the guide sleeve, and a second seal (S2) providing radial seal is provided between the valve needle (222, 322) and the guide sleeve.

3. The electronic expansion valve according to claim 2, characterized in that, The first seal (S1) is partially disposed in the pressing block (223, 323) and thus moves axially as the pressing block moves axially, and / or, the second seal (S2) is partially disposed in the valve needle (222, 322) and thus moves axially as the valve needle moves axially.

4. The electronic expansion valve according to claim 1, characterized in that, The pressing block (223) forms an arc surface at its first end facing the valve needle, in the state where the pressing block moves away from the valve needle, the fluid chamber is formed between the arc surface and the surface of the valve needle opposite to the arc surface; Or The pressing block (323) forms a flat surface at its first end facing the valve needle, and the pressing block has a recess opening towards the valve needle, the flat surface is located radially outside the recess, in the state where the pressing block moves away from the valve needle, the fluid chamber is formed between the flat surface and the recess and the surface of the valve needle opposite to the first end.

5. The electronic expansion valve according to any one of claims 1 to 4, characterized in that, The guide sleeve (321) includes a first section (321a) and a second section (321b), the inner diameter of the second section being larger than that of the first section, so as to form a step portion (328) between the first section and the second section, and the step portion is configured to limit the maximum distance that the pressure block (323) can move towards the first section (321a).

6. The electronic expansion valve according to claim 1, wherein The fluid passages (226, 326) axially pass through the valve needles (222, 322) and are formed in the center of the valve needles.

7. The electronic expansion valve according to claim 1, wherein The electronic expansion valve includes a first pipeline (252) and a second pipeline (254), and either one of the first pipeline and the second pipeline serves as an inlet pipeline and the other one of the first pipeline and the second pipeline serves as an outlet pipeline.

8. The electronic expansion valve according to claim 7, wherein The guide sleeve (321) is provided with passages (225, 325) that can fluidly connect the elastic element chambers in the guide sleeve where the elastic elements (224, 324) are arranged to the first pipeline and the second pipeline, The first pipeline (252) and the valve needle assembly (220, 320) are arranged on opposite sides of the valve seat (230).

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